This invention relates to cooling systems for condensing the exhaust steam of steam turbine plants, particularly of power plants.
Cooling systems of the above specified type generally consist of a mixing condenser connected to the outflow of the steam turbine of the plant and of a cooling tower connected to the cooling water circuit of the mixing condenser. So called dry cooling towers circulate the cooling or return water of the mixing condenser of the steam turbines through the water side of an air-water heat exchanger and perform the cooling by means of air introduced from the ambient. Their employment in case of power plants at arid sites is particularly advantageous. Then cooling effect is determined by the dry temperature of air which sets limits to cooling performance. In especially warm environments the cooling performance may fail to meet the cooling requirements of the power plant and, thus, may entail a reduction of its output.
The main object of the present invention is to avoid such deficiencies and to provide a cooling system the dry cooling tower of which is capable to reliably meet the cooling requirements even at especially high ambient temperatures without the necessity of increasing the size of the cooling tower. This is obtained by complementing the dry cooling with wet cooling if necessary where the cooling effect is determined by the wet temperature of air. Such temperature may be substantially lower than the dry temperature of air and, thus, may yield relatively much higher cooling effects.
The complementary wet cooling is ensured by a wet cooling apparatus arranged inside the cooling tower.
Dry cooling towers with interior wet cooling apparatus are already known. Such system is described e.g. in the specification of Hungarian patent No. 193 135. For warming up the air flowing through the wet cooling apparatus a tunnel-like box is provided inside the cooling tower, the inlet opening of which opens into the ambient while its outlet opening opens into the space inside the cooling tower. The wet cooling apparatus is located between these two openings. However, the system described there is but moderately suitable to increase the cooling effect at good efficiency. Viz., the air current cooled by the dry heat exchangers--hereinafter called "main" heat exchangers--of the cooling tower becomes mixed inside the cooling tower with the air exiting from the wet cooling apparatus. As is known, such mixing entails, as a rule, decreased resultant air temperatures by which the draft of the cooling tower deteriorates and its cooling action diminishes. In extreme cases the additional or complementary cooling action of the wet cooling apparatus may entirely be impaired.